Beverage preparation machines that inject pressurized fluid into a capsule are well-known, especially in the field of producing coffee beverages, typically from roast and ground coffee. In addition, other substances such as chocolate, tea or milk products can be extracted or dissolved to form a beverage, from ingredients which are for instance soluble powders. The advantages of such a system are in particular the conservation and freshness of the ingredients, as well as the possibility of facilitating the operations of preparing the beverage.
The method of preparing the beverages using such a device is in principle as follows. The capsule is usually first inserted into a receiving brewing chamber of the beverage preparation device. After that, a water injection means, such as a needle connected to the liquid supply of the device and which projects inside the brewing chamber, is introduced through a face of the capsule to inject a hot or cold/ambient liquid, in order to make the liquid interact with the ingredients within the capsule. The liquid beverage resulting from this interaction is then discharged through a delivery face of the capsule. For example, the delivery face opens due to the internal pressure in the capsule generated by injecting the liquid, as described in applicant's European patent EP 1472156 B1.
It should be understood that the interaction between the liquid and the ingredients within the capsule can be e.g. dissolving, extraction, brewing or any other interaction in order to prepare a beverage by means of ingredients provided within the capsule.
In FIG. 1, a typical beverage preparation machine 1 is illustrated, which comprises a water reservoir 2, a brewing head 3, a cup tray 4 that can be set at different heights relative to the brewing head, control panel and buttons 5. In a possible embodiment, the control buttons comprise more particularly a rotating wheel 6 and the control panel is a screen 7. An ingredient capsule can be placed in a capsule holder 8 which is removably inserted into the brewing head 3. The screen 7 is suitable for displaying various information to the consumer, for instance the volume level 9 that is dispensed in the cup. The user can also choose the temperature of the beverage that will be prepared, by actuating hot or cold buttons 11 which are present close to the wheel and screen on the surface of the brewing head.
FIG. 2 represents schematically the internal configuration of an embodiment of a brewing head 3 in its open position. The capsule holder 8 is loaded with a capsule 12. The capsule has a top pierceable membrane 13, and top peripheral edge 14. The brewing head 3 typically comprises an open/close mechanism with a handle 15 and a knee mechanism 16 that mechanically links the handle to a support plate 17. The support plate 17 carries an injection plate 18 that is moved in direct contact with the peripheral edges 14 and top membrane 13 of the capsule in a leaktight manner, when the brewing head is in the closed position. The injection plate is preferably a needle plate that carries at least one injection needle 19 to pierce through the top membrane of the capsule when the brewing head is closed. The needle 19 is linked in a fluidic manner (via pipes) to the pump, heating element, and reservoir (elements not shown in the drawing) of the machine. Further details of a possible construction are disclosed in applicant's European patents EP 1967099 B1 or EP 1967100 B1.
Generally, machines for applying the principle of beverage production described above, use water for mixing with the beverage ingredients, hence scaling of the device or in particular within the needle plate can affect their functionality. Further, the needle plate is likely to be subjected to residua of dissolved or solid substance from the capsule, e.g. pierced or otherwise injected, such as coffee or the like, by a so-called “backflow” effect due to residual pressure within the capsule after the beverage was prepared and dispensed. More precisely, during backflow, small quantities of remaining beverage formed within the capsule and still under pressure therein even after most of the beverage has been released from said capsule, can flow back through the needle and leak in the surroundings of the needle plate.
Such residues and limescale are illustrated in FIG. 3, which shows the upper surface of the injection plate 18. As can be seen, limescale and residues “LSR” cover the needle plate upper surface, all around the needle upper rubber coupling 20 with the machine fluid pipes (not shown in FIG. 3).
As the needle for piercing the capsule has a small diameter, cleaning of said needle should be regularly carried out in order to ensure a correct functioning of the injection and particularly to prevent the needle from being blocked by scaling or by a substance provided within a capsule to be introduced, e.g., pierced or otherwise injected, by the needle. Moreover, it was observed that due to the backflow, the upper surface of the injection/needle plate tends to gather residues of beverage. And in addition to the ingredient residues that can accumulate on top of the injection/needle plate, it was found that due to the fact that the needle plate is made of metal, the temperature of the latter is low, and condensation tends to form from water vapour escaping the machine and the cup placed underneath, such that after some time, the upper surface of the needle plate is covered with limescale. Both residues and limescale are of course highly undesirable, and require regular cleaning, descaling, and maintenance of the needle plate, to ensure a proper, safe, and hygienic functioning of the machine.
For security reasons, the injection plate (i.e. the injection plate carrying the injection needle) was placed within a housing of the beverage preparation device itself, more precisely, as a part of the brewing head, so as to reduce the risk of getting in contact with the injection needle during the process of beverage preparation to a minimum extent, as described in EP 2071988 B1.
As described in EP'988, the needle plate was designed to be removed from the rest of the machine brewing head, to allow said needle plate and needle channel to be cleaned and descaled. However, this disassembling operation tends to be complex and, to some extent unsafe for the consumer, who still has to manipulate the needle plate with its protruding needle.
The objective of the present invention is to provide a beverage preparation machine having a brewing head and injection plate for injecting a liquid under pressure in a capsule that can be cleaned and descaled, without the need for a disassembling operation.